Both intertidal area and subtidal areas
Subtidal area only
Intertidal area only
On the beach
Algae
Other sea urchins
Sea cucumbers
Small fish
Dome
Porcupine
Pentamerous
Toothpick
Because a sea urchin's egg is relatively big
Because sea urchins have large numbers of eggs
Because sea urchins have large numbers of relatively big eggs
Because the eggs make great omlettes
Nose
Mouth
Spine
Feet
Animalia
Strongylocentrotus
Purpuratus
Echinoderms